US4030351A - Method and apparatus for laboratory testing of carburetors - Google Patents

Method and apparatus for laboratory testing of carburetors Download PDF

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Publication number
US4030351A
US4030351A US05/633,022 US63302275A US4030351A US 4030351 A US4030351 A US 4030351A US 63302275 A US63302275 A US 63302275A US 4030351 A US4030351 A US 4030351A
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pressure
carburetor
fuel
test
manifold vacuum
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US05/633,022
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English (en)
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Richard Lawrence Smith
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SCANS ASSOC Inc
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SCANS ASSOC Inc
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Priority to US05/633,022 priority Critical patent/US4030351A/en
Priority to GB36813/76A priority patent/GB1548953A/en
Priority to IT51977/76A priority patent/IT1075996B/it
Priority to DE2649682A priority patent/DE2649682C2/de
Priority to JP51131570A priority patent/JPS5275465A/ja
Priority to BE172319A priority patent/BE848293A/xx
Priority to CA265,673A priority patent/CA1075493A/en
Priority to FR7634508A priority patent/FR2331784A1/fr
Priority to AU19703/76A priority patent/AU496906B2/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M19/00—Details, component parts, or accessories of carburettors, not provided for in, or of interest apart from, the apparatus of groups F02M1/00 - F02M17/00
    • F02M19/01—Apparatus for testing, tuning, or synchronising carburettors, e.g. carburettor glow stands

Definitions

  • This invention relates to a method and apparatus for laboratory testing of carburetors to determine the air/fuel ratio thereof, and more particularly to a completely automated apparatus for performing such testing.
  • the pneumatic throttle positioner was replaced with an electric throttle positioner which could arrive at the desired manifold vacuum much more quickly.
  • the multiple critical venturi meters previously used were replaced with variable area critical venturi meters.
  • the first type of test involves the laboratory testing of the carburetor at many test points, each specifying a manifold vacuum, air flow, and hood pressure, and determining the mass air flow rate and mass fuel flow rate at the specific point to arrive at an air/fuel ratio.
  • the second type of test is what is known as a "Balanced Box" carburetor test, in which at all test points other than at idle and wide open throttle, the manifold vacuum present is a function of the characteristics of the vacuum pump.
  • the third type of carburetor test is the constant manifold vacuum test in which one would flow at a single manifold vacuum for all test points, with the only flexibility being that of different throttle positions.
  • the carburetor throttle plate is set at a desired position such as idle, and an air flow is established through the carburetor until the desired manifold vacuum is reached. At this point the mass flow rate of air can be determined by the differential pressure across the carburetor and once this is obtained the air/fuel ratio could be measured.
  • an all pneumatic stand was used, and the air flow was established through seven or eight subsonic nozzles which had to be used one at a time in connection with individual scales on an inclinometer, with the differential pressure across each nozzle being read on said inclinometer.
  • Such a stand had no hood pressure control so that not tests at altitude could be made, and all tests were of the Balanced Box type. Obviously such a stand offered little flexibility, was slow in operation, and because it was pneumatic, was difficult to work with due to the sensitive nature of the pneumatic measuring devices.
  • the setting of hood pressure involved the setting of air flow through a valve operated by a controller, and since said valve and controller mechanism had to be able to operate quickly when any changes in hood pressure occurred which were required by the test points of the carburetor, and further since air measurement is a difficult process to control, the controllers used in the old system were what is known as three-mode controllers in which the air flow through the hood pressure measurement and control system of the test stand was controlled through a combination of proportional, reset, and rate control. While such terms will be described further later in the specification, it can not be over emphasized that since a combination of all three modes of control were made, the control of air flow presented a most difficult problem in the art.
  • each test point will have optimum values of rate, reset and proportion which would correct the upset in the system as quickly as possible.
  • the lack of optimum values for each test point is even more serious in the manifold vacuum control system than it is in the hood pressure control system as two valves, a manifold vacuum in-line valve with a three-mode controller and a manually operated bypass valve, to be described in more detail later, are customarily used.
  • the hood pressure will also change, thus it is even more critical in manifold vacuum control area to be able to supply new values of rate, reset, and proportion to the controllers for each test point.
  • one of the objects of the present invention is to provide an improved method and apparatus for the laboratory testing of carburetors whereby the above difficulties and disadvantageous are overcome and largely eliminated, and a much simplier and faster and more accurate carburetor testing system is thus produced at a reasonable cost.
  • Another object of the present invention is to provide a carburetor testing system which is capable of testing carburetors rapidly at several points within their operating range quickly and accurately.
  • Another object of the present invention is to test carburetors in the above mentioned manner and provide a system for controlling the manifold vacuum in the carburetor at each test point which is accurate and which can establish different manifold vacuum through the carburetor in a rapid manner.
  • a further object of the present invention is to provide a manifold vacuum measurement and control system for laboratory testing of carburetors in which the establishment of the manifold vacuum through the carburetor is aided by the in-line and bypass valves being controlled by three-mode controllers.
  • a still further object of the invention is to provide that the three-mode controllers for the in-line and bypass valves have the capability of multiple predetermined settings of rate, reset and proportion so that any upset in the manifold vacuum measurement and control system can be dealt with in the most rapid manner possible.
  • a still further object of the present invention is to provide for the three-mode controllers of the present invention to be assisted by a computer so that the optimum settings of rate, reset and proportion will be provided to the controllers for each test point in the operating range of the carburetor being tested.
  • Another object of the present invention is to provide a laboratory carburetor test stand having a manifold vacuum measurement and control system of the above described nature.
  • Another object of the present invention is to provide the test stand described above with a hood pressure control system wherein the controller used in such system is a three-mode controller having the capability of multiple settings of rate, reset, and proportion, and further providing that such system is computer assisted so that optimum values of rate, reset and proportion are supplied to the controller for each test point.
  • a still further object of the present invention is to provide a laboratory test stand having, in addition to the hood pressure and manifold vacuum measurement and control systems, air flow and fuel flow control systems, all of which are computer assisted and are unified into a complete laboratory carburetor test stand having the purpose of providing accurate determinations of the air/fuel ratio of a test carburetor at multiple test points in a most accurate and rapid manner.
  • a still further object of the present invention is to provide the unified test stand described immediately above which by virtue of computer control makes the supplying of optimum values of rate, reset, and proportion for each carburetor test point feasible, is relatively inexpensive, and is dependable in operation.
  • FIG. 1 is a perspective view of a test stand embodying the construction of the present invention.
  • FIG. 2 is a partial cut-away view of the test stand shown in FIG. 1 with the control panel thereof shown on a larger scale.
  • FIG. 3 is a perspective view of the area under the hood of the test stand of FIG. 1, showing a carburetor mounted in the test stand for the purposes of testing and adjusting thereof.
  • FIG. 4 is an overall diagrammatic view of a test system embodying the construction of the present invention and showing as subsystems thereof systems to control the hood pressure, air flow, manifold vacuum, and fuel flow.
  • FIG. 5 is a diagrammatic view of a system substantially similar to that shown in FIG. 4, but being intended for use in a room where the environment is controlled to produce the desired test conditions.
  • FIG. 6 is a diagrammatic view showing the manifold vacuum measurement and control system as it may be used in FIGS. 4 or 5.
  • FIG. 7 is a diagrammatic view of the control circuit enclosed in the dotted lines in FIG. 6.
  • FIG. 8 is a view substantially similar to that of FIG. 6 wherein the manifold vacuum bypass valve is adapted for computer operation.
  • FIG. 9 is a diagrammatic view of the hood pressure control system as it may appear in the construction of FIG. 4.
  • FIG. 10 is a partial view showing the changes needed in the construction shown in FIG. 9 for the hood pressure control system to be used in the apparatus shown in FIG. 5.
  • FIG. 11 is a diagrammatic view of the air flow measurement and control system as shown in FIG. 4 utilizing laminar flow tubes to measure the air flow.
  • FIG. 12 is a partial diagrammatic view showing the interchanging of the laminar flow tubes and hood pressure valve shown in FIG. 11 to adapt the air flow measurement and control system shown therein for use in the system of FIG. 5 in a controlled atmosphere room.
  • FIG. 13 is a partial diagrammatic view showing the substitution of subsonic nozzles for the laminar flow tubes shown in FIG. 11.
  • FIG. 14 is a view substantially similar to FIG. 13, except showing the position of the subsonic nozzle and the hood pressure valve as being reversed for use in the system shown in FIG. 5.
  • FIG. 15 is a diagrammatic view of the fuel flow measurement system as shown in FIGS. 4 and 5, and embodying a mass flow transducer for use in controlling and measuring fuel flow.
  • FIG. 16 is a diagrammatic view showing a modification of the fuel flow measurement system shown in FIG. 15 with orifices being used in place of the mass transducer to measure the rate of fuel flow, and showing in addition apparatus for fuel pressure control and fuel temperature measurement.
  • FIG. 17 is a partial diagrammatic view of a modification of FIG. 16, wherein a volume flow transducer is used in place of the orifices for the measurement of fuel flow.
  • FIG. 18 is a graph showing the relationship between the percentage opening of a valve and the air flow through the valve.
  • FIG. 19 is a graph showing the effect of low, correct and high settings for the proportional band of a three-mode controller.
  • FIG. 20 is a graph showing the effects of the low, correct or high settings for the reset times on a three-mode controller.
  • FIG. 21 is a graph showing the effect of the low, correct or high settings of a derivative time on a three-mode controller.
  • FIG. 22 is a graph corresponding in part to FIG. 19 and showing the effects of choosing too wide, too narrow and correct proportional bands on a difficult to control process, and the resulting offset which occurs.
  • FIG. 23 is a graph of the effects of choosing too short, too long and the correct reset time in a process having a proprotional plus reset control.
  • FIG. 24 is a graph of the effects of choosing too short, too long, and correct derivative time shown on a proportional plus reset plus derivative controller.
  • FIG. 25 is a graph showing the difference in recovery time between a two-mode controller and a three-mode controller.
  • FIG. 26 is a graph corresponding to that shown in FIG. 25 with the two curves superimposed on each other for better comparison.
  • FIG. 27 is a graph showing the relationship between valve position and change in measurement for different values of proportional band.
  • FIG. 28 is a drawing of a flow chart showing one of the methods that a carburetor laboratory test stand embodying the construction of the present invention may use to perform a test at a specific manifold vacuum and hood pressure.
  • the present invention is embodied in a test stand generally designated by the numeral 25.
  • the test stand consists of a flow stand portion 26 generally shown as the right hand portion of FIG. 1, and a console section 27, which would constitute the left hand portion of FIG. 1.
  • a computer 28 having provisions for operation with cassette memory 29.
  • the computer has connected to it a remote terminal 30 for reports indicating the results of the tests performed by the stand 25, and calibration of the stand itself.
  • apparatus as generally designated by the numeral 33 for controlling the position of the carburetor throttle during the test.
  • Such apparatus includes a display 34 for displaying the angular position of the throttle, and also a set of push buttons 35 for use when manual control of the carburetor throttle is desired.
  • a second control panel generally designated by the numeral 36, which has a series of push button switches which control the supplying of power to subsystems such as the vacuum system, fuel system, the power to the carburetor, etc.
  • the upper control panel 37 has several portions, among them a dedicated display 39 upon which will appear the value for air flow at any given time, and four sets of push buttons as identified by the numerals 40-43.
  • the first set of push buttons 40 determines whether the carburetor throttle is to be manually operated by the push buttons 35, or is to be computer controlled.
  • the second set of push buttons 41 determines whether the manifold vacuum in the stand is to be controlled by the computer, or manually by the potentiometers 50 and 51 which are used to set the manifold vacuum and manifold vacuum bypass valve respectively.
  • the third set of push buttons 42 is used to determine whether the hood pressure is controlled automatically by the computer 28, or manually by the hood pressure potentiometer 52.
  • the fourth set of push buttons 43 is used to determine whether the operating mode of the test stand is manual, computer-manual, computer, or calibration.
  • a generalized display 44 which is adapted to display whatever function is chosen by the display function switches 45 and 46.
  • a keyboard 53 which, together with the associated buttons 54 and 55 provides for the test stand operator to enter the desired test parameters into the computer 28.
  • the air flow control buttons 56 select whether the air flow will be computer controlled or manually controlled by the operator, and the associated percent air flow meter 57 informs the operator what percent of maximum air flow the test stand is operating at.
  • a similar set of controls is provided for fuel flow by the fuel flow buttons 58, enabling the operator to choose whether the fuel flow control is computer controlled or manually controlled by the operator.
  • the associated percent fuel flow meter 59 informs the operator what percent of the maximum fuel flow is occurring at any given time.
  • a hood pressure gauge 60 to inform the operator on a continuous basis what the absolute pressure is under the hood 68.
  • a fuel pressure regulator 62 and a fuel pressure gauge 61 combine to enable the test stand operator to regulate the fuel pressure at the carburetor at all times, while for convenience of the operator when changing carburetors, a manual manifold vacuum shut-off valve 63 enables him to change carburetors without continuously shutting off the vaccum pump (not shown).
  • hood 68 reciprocally movable in a vertical direction by means of the hydraulic cylinders 69.
  • the hood 68 which is adapted to enclose a suitable test chamber 88 in the lowered position has a glass section 70 to enable the operator to look into the test chamber when the carburetor test is taking place.
  • the hood 68 in its lowered position sealingly engages the plate 71 to define a suitable test area thereunder.
  • a riser 72 on which is mounted a carburetor 73 to be tested.
  • Fuel enters the carburetor 73 by way of the fuel line 74, which is output of the fuel flow measurement system shown in FIGS. 4, 5, 15 and 16.
  • a carburetor throttle positioner 76 connected to a power source with an appropriate electric wire 77.
  • FIG. 4 A basic system embodying the construction of the present invention is shown in FIG. 4.
  • the carburetor 73 would be mounted under hood 68, in the manner previously described, to the riser 72.
  • the hood 68 would then be lowered to sealingly enclose the test chamber indicated by the numeral 88.
  • the next step in a carburetor test utilizing the present invention is to cause the manifold vacuum measurement and control system 89 to cause air to flow from the air supply (controlled room or supply system) through the hood pressure measurement and control system generally designated by the numeral 90, through the air flow measurement and control system generally designated by the numeral 91, and through the conduit 92 to the interior of the test chamber 88.
  • the air flows through the carburetor 73, the conduit 93, through manifold vacuum measurement and control system 89 by means of the conduit 94 to a vacuum source (not shown), and ultimately to the atmosphere.
  • Air flowing through the carburetor 73 draws fuel into the carburetor from the fuel line 74 which is connected to the fuel flow measurement system 75. This, in turn, is connected to the fuel supply (not shown).
  • the vacuum source is normally a vacuum pump of which there are many on the market.
  • Any vacuum pump may be used providing that it is of size sufficient to produce the air flow necessary through the carburetor being tested so that all desired tests can be run.
  • the air supply system need only be a source of air which is being controlled as to temperature, pressure, and humidity.
  • Many air supply systems are available, and again, any supply system may be used, provided it is of a sufficient capacity to flow the desired amount of air through the carburetor being tested so that such carburetor may be tested under all desired conditions.
  • this is essentially a fuel pump which can supply fuel at a desired pressure and temperature in sufficient volume so that the particular carburetor being tested can be run at any point of its operating range.
  • any of several such fuel supply systems may be used.
  • the manifold vacuum measurement and control system 89 has caused air to flow through the carburetor 73.
  • the pressure under the hood 68 be set at sea level by the hood pressure system 90, and kept constant at all test points.
  • the air flow measurement and control system will cause the throttle plate in the carburetor to be rotated by the throttle positioner 76 until the desired air flow is present through the carburetor.
  • the third type of carburetor test that I am aware of would be the constant manifold vacuum test, in which one would flow at a single manifold vacuum for all test points, with the only flexibility being the different throttle positions.
  • system of the present invention is adapted to be used both in a system as shown in FIG. 4, where an air supply system is available to supply air at a desired pressure, air temperature and humidity, or as shown in FIG. 5, where the system is adapted to be used in a controlled environment room where the same parameters of air pressure, temperature and humidity are controlled.
  • proportional control is one in which there is a continuous linear relation between the value of the controlled variable, in this case air flow, and the position of the final control element, which in this case would be the valve.
  • Proportional control action operates the controller according to what is called a proportional band and this band expressed in percentage is the range of values of the control variable which corresponds to the full operating range of the valve. For example if a 50% change in the air flow would cause the valve to go from a fully closed position to a fully open position it is said that there is a 50% proportional band. In processes which are easy to control a proportional control is sufficient, but the proportional band must be chosen carefully.
  • FIG. 19 shows the importance of choosing the correct porportional band.
  • the system will cycle as shown by the curve labeled A if too low a proportional band is chosen. If too high a proportional band is chosen you will have a large and prolonged deviation from your desired value or set point, as shown by the curved labeled C in FIG. 19, while with the correct value, as shown by the curve labeled B, you will have the quickest return to the set point after the system experiences an upset.
  • proportional control for instance in a temperature control system, there is a temperature corresponding to each position of the control valve.
  • the process will stabilize at any temperature within the proportional band.
  • a proportional band of 10% the valve is open at 45% of the measurement span and closed at 55%.
  • the process can stablilze at any temperature between these limits and this results in a problem called offset, as the system can stabilize at a value several degrees different than the original temperature.
  • Proportional plus reset plus derivative controllers are often termed "Three-mode Controllers" and are the type used in the present invention.
  • Derivative control action is proportional to the rate of change of measurement and causes the control valve to reach a correct position sooner than with a Two-mode Controller. In essence the addition of the derivative control action helps the system to anticipate changes.
  • the effect of derivative action alone is shown in FIG. 21, again with the causes labeled A, B and C representing the effect of a too low, correct, or too high derivative time.
  • the proportional plus reset plus derivative curves are shown in FIG. 24, which provides the fastest possible recovery time.
  • the choice of the proper derivative time is critical, because the choice of a too long derivative time, represented by the curve labeled X, will again cause the system to cycle.
  • the choice of too short a time, represented by the curve labeled Z, will cause too large a deviation from the set point, while the curve labeled Y will have the optimum response time.
  • FIGS. 25 and 26 The difference in time between the system with proportional and reset control only, and porportional and reset control with derivative action is dramatically illustrated by FIGS. 25 and 26.
  • the recovery time for a Two-mode Controller is represented by the recovery curve labeled "proportional and reset" in FIG. 25, and the recovery time is represented by T2, while the recovery time of a Three-mode Controller is represented by the "proportional, reset and derivative" curve, and the recovery time is represented by T3. It can be seen that T3 is approximately one-half of T2. For better comparison, these curves are superimposed in FIG. 26.
  • the manifold vacuum can be defined as the pressure across the carburetor, and is usually measured as the differential pressure between two points, the first being at a point inside the test chamber 88, and the second at a point in the carburetor riser 72, this measurement is performed by differential pressure transducer 103.
  • the signal from the differential pressure transducer 103 which is normally a current signal, is supplid to the signal conditioner 104 where it is continuously converted into a voltage signal which is then supplied to an A/D (analog-to-digital) converter 105 where it is converted into a digital signal, which is supplied to the computer interface 97, and from there is transferred to the computer 28.
  • the signal that the computer 28 has received can now be used for the calculation of the actual manifold vacuum.
  • manifold vacuum it is customary to use two valves, one being the manifold vacuum in-line valve 107 and the other being the manifold vacuum bypass valve 108.
  • the bypass valve is generally used to establish the maximum vacuum which can be obtained, while the manifold vacuum in-line valve is used to adjust the manifold vacuum to the one vacuum required.
  • the computer uses the value of the manifold vacuum as previously calculated in determining the desired position of the manifold vacuum in-line valve 107.
  • the computer then supplies a signal to the computer interface 97, which in turn supplies this signal to the D/A convertor 106.
  • the voltage signal is supplied to the E/I transmitter 110 which converts this signal into a current signal which is fed to the I/P transmitter 109.
  • the pressure signal from this transmitter is supplied to a positioner which is a part of the manifold vacuum in-line valve 107.
  • the position of this valve is directly controlled by the signal which is supplied to the positioner. As an example, when a signal of three PSI is supplied to the positioner the valve is fully open, while a pressure of 15 PSI results in the valve being fully closed.
  • this valve be used in the center operating area normally between approximately 20% open and 90% open. Referring to FIG. 18 it is seen that if the valve is used at less than 20% open, small changes in the pressure signal from the I/P transmitter 109, corresponding to small changes in the valve opening, result in small manifold vacuum changes which are large percentage changes thus resulting in a manifold vacuum signal which is not stable. If the valve is used at a position greater than 90% open, changes to the pressure signal supplied to the positioner have little effect on the manifold vacuum, and thus the response is extremely slow. For this reason we use the manifold vacuum bypass valve 108 as an adjustment to keep the manifold vacuum in-line valve 107 operating in the desired range.
  • the voltage signal from the first manifold vacuum D/A converter 106 is also supplied to the control circuit 113.
  • the output of the control circuit is an analog voltage signal which is supplied to the second manifold vacuum E/I transmitter 112, which converts the voltage into a current signal which is then supplied to the second manifold vacuum I/P transmitter 111.
  • the pressure output from this transmitter is supplied to the positioner which is a part of the manifold vacuum bypass valve 108.
  • I/P transmitter when used, what is meant is a current to pressure converter. This item need not be discussed in detail because it is well known in the art, and a I/P transmitter that may be used in the present invention is the Model No. 69TA made by the Foxboro Company, Foxboro, Massachusetts.
  • E/I transmitter when the term E/I transmitter is used, what is meant is a voltage to current converter, which also may be one manufactured by the Foxboro Company, such as their Model No. 66G.
  • I/P and E/I transmitters will be shown in many places throughout the description of the various figures of the drawings. However, in the case of these two transmitters, unlike the A/D and D/A converters, a separate transmitter is needed wherever shown, as unlike the D/A converter, wherein the converter may be of a multiplexing type, such a substitution is not possible in this case, and although all the I/P and E/I transmitters illustrated may be identical, they will carry separate numbers as physically separate transmitters are needed. The same holds true of the signal conditioners.
  • the A/D multiplexing type of converter is possible in this test stand because the computer operates at such a rapid speed that it is able to sense the signals of the various signal conditioners at such a rapid rate that no error is caused.
  • the signal supplied to the I/P convertr it is required that a pressure be available to the valve positioner all of the time or else the valve position will change causing errors in the stand operation.
  • the control circuit 113 is shown in more detail in FIG. 7.
  • Voltage signals from the dual analog limits 117 such as can be provided by potentiometers manufactured as Model No. 7216 by Beckman Instruments, Inc. of Fullerton, California, are supplied to the dual analog comparator 119.
  • the dual limits represent the desired working range of the manifold vacuum in-line valve 107. As described previously, these limits might be for example between 20% and 90% open. It should be recognizd that at the different conditions over which air flow is measured, it might be desirable to have a different set of dual limits for each air flow measurement sensor, in which case the limits provided to the dual comparator would be set for the particular air flow range in use.
  • the voltage signal from the first manifold vacuum D/A converter 106 is also supplied to the dual comparator 119. If the input voltage is within the desired working range, then both outputs from the dual comparator are at a low TTL (transistor-transistor logic) level. If the input voltage is at a level indicating that the valve position is not sufficiently open a high TTL output is supplied to the first NAND gage 120. The output of the NAND gate is a low level TTL signal which is supplied to the up-down counter 123, such as Model No. 30015, manufactured by Scans Associates, Inc., Livonia, Michigan.
  • the low level signal from the first NAND gate 120 is also supplied to the third NAND gate 122, which functions as an OR gate, in supplying a high level enable signal to the up-down counter.
  • the up-down counter then utilizes the pulses which are provided by the oscillator 118 and proceeds to count in an increasing direction. It should be recognized that, as with the dual limits, it might be desirable to have a different oscillator frequency for each air flow measurement sensor.
  • the output of the up-down counter is a binary TTL logic level signal which is supplied to a dedicated D/A converter 124. As the count on the counter increases, the analog output voltage to the dedicated D/A converter increases also, which in turn increases the pressure supplied to the manifold vacuum bypass valve 108, which causes the valve to change position.
  • the manifold vacuum signal When this valve position changes, the manifold vacuum signal, as sensed by the differential pressure transducer 103, causes the manifold vacuum to change. This change in vacuum is supplied to the computer 28 as described above. As shown in FIG. 6, the computer senses the change in manifold vacuum and provides a different output signal which changes the pressure supplied to the manifold vacuum in-line valve 107 until the valve is in the desired range. At this time, the analog signal from the first manifold vacuum D/A converter 106, which is supplied to the dual comparator 119, is within limits, and the output signal of the comparator again becomes a low TTL signal. This in turn changes the output from the first and second NAND gates, 120 and 122 respectively, causing the up-down counter 123 to stop counting.
  • a high level output signal would be supplied to the third NAND gate 122 and would cause the up-down counter 123 to count in the opposite direction and change the output of the dedicated D/A converter 124, causing the manifold vacuum bypass valve 108 to change its position until the manifold in-line valve 107 was once again in the desired operating range.
  • a set of dual digital limits 126 is also provided for checking the output of the up-down counter 123. The dual limits 126 are both supplied to the dual digital comparator 125.
  • the output signal from the dual digital comparator becomes a low TTL signal, causing the NAND gates, 120 or 122 to have a high output signal, in turn causing the up-down counter 123 to stop further counting in that direction.
  • This causes the analog voltage to the dedicated D/A converter 124 to remain constant, which prevents further movement of the valve 108 in the same direction.
  • the manifold vacuum is substantially controlled in a similar manner as that shown in FIG. 6, except that the manifold vacuum bypass valve 108 is also controlled by the computer.
  • the computer 28 provides an output signal to the computer interface 97, which in turn provides a signal to a second section of the manifold vacuum D/A converter 106.
  • the output of this D A converter is a voltage signal which is supplied to the second manifold vacuum E/I converter 112, and the current from this converter is used as described previously.
  • additional computer interface hardware and computer programming is required to make the system operate substantially the same as previously described.
  • the hood pressure measurement and control system 90 is shown in more detail in FIG. 9. This system is used in controlling the pressure in the test chamber 88. When this pressure is less than ambient pressure, it is sometimes referred to as altitude.
  • the pressure in this chamber is sensed by an absolute pressure transducer 135 such as Model No. 1105, manufactured by Rosemount Engineering Co. of Minneapolis, Minnesota.
  • the output of this transmitter is a voltage signal which is supplied to a hood pressure signal conditioner 134, whose output in turn is supplied to the hood presure A/D converter 105.
  • the digital output of this converter is sent to the computer interface 97, and then to the computer 28.
  • the computer utilizes this signal in calculating the value of the hood pressure.
  • Hood pressure is controlled by the operation of the hood pressure valve 133.
  • the position of the valve is controlled by the computer 28 which provides a signal based on the optimum value of rate, reset and proportion for the particular test point to the computer interface 97 which in turn provides a digital signal to the hood pressure D/A converter 106.
  • the voltage output of this converter is sent to the hood pressure E/I transmitter 131 to convert this voltage to a current that is supplied to the hood pressure I/P transmitter 132.
  • the air pressure supplied from the I/P transmitter is supplied to the positioner which is a portion of the hood pressure valve 133.
  • the valve 133 sets the hood pressure in a manner similar to that just described for the manifold vacuum valve 107.
  • the operation of the system as shown in FIG. 10 is substantially the same. In this case the hood pressure valve 133 and air flow measurement sensors 136 are reversed when used in a controlled environment room.
  • a controller such as Model 62-H manufactured by the Foxboro Company of Foxboro, Massachusetts is used in conjunction with pressure transmitters, the signal conditioners, the I/P transmitters, and the hood pressure and manifold vacuum in-line valves.
  • One controller is used for manifold vacuum in-line valve control and a second controller for the hood pressure valve control.
  • These controllers are of a type frequently used for control of valves and include the capability of setting in single values for the three terms proportional, reset, and rate (or derivative).
  • the amount of proportion that is set is used in determining the factor by which the output signal to the valve changes in proportion the difference between the desired set point and the actual hood pressure or manifold vacuum sensed by the transducer.
  • the reset capability is used to keep shifting the set point gradually and thus force the controller to follow the set point until the desired point has been reached.
  • the rate action is used when its desired to anticipate the process change because the process does not respond rapidly.
  • Determining the optimum setting of the three terms is a very time consuming process making it unfeasible for an operator to continually change these settings while a test is in progress. While it would be possible to design a system that would have the potential for setting the terms proportional, reset, and rate for a varity of test conditions, in reality this is not feasible because the expense of designing a special system would also require detailed analysis of the hood pressure, manifold vacuum, and air flow conditions in order to determine the desired setting each of the three terms. The number of settings that would be required would also need to be determined. In this invention, utilizing the computer 28 I have included a controller type operation which contains the capability of establishing the proportion, reset, and rate settings as a function of the actual and desired value of hood pressure, manifold vacuum, and air flow.
  • the first step which occurs in the carburetor test is to calculate for the particular test stand the values of proportional band, reset time and derivative time for each of the control valves such as the manifold vacuum in-line valve 107, the manifold bypass valve 108 when this valve is to be operated by the computer, and the hood pressure control valve 133.
  • the control valves such as the manifold vacuum in-line valve 107, the manifold bypass valve 108 when this valve is to be operated by the computer, and the hood pressure control valve 133.
  • the control valves such as the manifold vacuum in-line valve 107, the manifold bypass valve 108 when this valve is to be operated by the computer, and the hood pressure control valve 133.
  • the above described step is a very important one as it provides the basis for the other operation in the carburetor test which will be described later, after a description of the air flow measurement and control system 91 and the fuel flow measurement system 75.
  • the air flow measurement and control system 91 is shown in FIG. 11. As the air passes through the laminar flow tubes 143 a differential pressure signal is provided which is proportional to the air flow through the laminar flow tubes. This differential pressure is sensed by the air flow differential pressure transmitter 142, such as Model No. 1151 manufactured by Rosemount Engineering Company which converts this signal into a current signal. The current is supplied to the air flow signal conditioner 139 converting the current into a voltage which is supplied to the air flow A/D converter 105 for conversion into a digital signal, which is supplied to the computer interface 97 and thence on to the computer 28.
  • the air flow differential pressure transmitter 142 such as Model No. 1151 manufactured by Rosemount Engineering Company which converts this signal into a current signal.
  • the current is supplied to the air flow signal conditioner 139 converting the current into a voltage which is supplied to the air flow A/D converter 105 for conversion into a digital signal, which is supplied to the computer interface 97 and thence on to the computer 28.
  • the laminar flow tubes are a volumetric device, and carburetor testing is normally done in mass flow units, it is also necessary that the temperature and absolute pressure of the air entering the flow tubes be known in order to calculate the mass air flow.
  • the temperature is sensed by the temperature transducer 140 such as Model NO. 410 as manufactured by Yellow Springs Instrument Company of Yellow Springs, Ohio.
  • the output of this transmitter is a resistance signal which is provided to the temperature signal conditioner 137 which converts the signal into a voltage signal.
  • This voltage is provided to an additional section of the air flow A/D converter 105 to be converted from an analog signal into a digital signal which is supplied to the computer interface 97, which in turn provides it to the computer 28.
  • the absolute pressure is sensed by an absolute pressure transducer 141 which converts the pressure into a voltage signal.
  • This voltage signal is supplied to the second air flow signal conditioner 138 whose output is supplied to an additional section of the air flow A/D converter 105, which in turn supplies a digital signal to the computer interface 97, and thence is supplied to the computer 28.
  • the computer utilizes the values of the differential pressure, absolute pressure, and temperature in calculating the actual mass air flow entering the carburetor. If this value is different from the desired air flow, the computer provides an output signal to the computer interface 97, which provides a TTL logic signal to the throttle circuit such as Model No. STM 1800 as manufactured by The Superior Electric Company of Bristol, Connecticut. The output provides the signal to the throttle positioner 76 causing the throttle plate 78 to move to the desired postion.
  • FIG. 13 is substantially the same in operation as FIG. 11, except subsonic nozzles 145 are used to measure the volumetric air flow instead of the laminar flow tubes 143. Since subsonic nozzles are also a volumetric flow device, it is necessary to know the absolute pressure and the temperature of the air entering the nozzles for the calculation of mass air flow. When these volumetric flow devices are used for measuring air flow, it is desirable that the pressure of the air entering the laminar flow tubes or subsonic nozzles be essentially constant.
  • the air measurement sensors are normally located upstream of the hood pressure valve 133. For this situation, the air flow measurement sensors are shown as 136 in FIG. 10, the laminar flow tubes 143 in FIG. 12, and subsonic nozzles as 145 when used in the system shown in FIG. 5.
  • the fuel flow measurement system 75 is shown in more detail in FIG. 15.
  • the fuel from the fuel supply is fed through a first pressure regulator 150 in order that a stable fuel pressure be provided to the fuel flow transducer.
  • the fuel flow transducer is a mass flow transducer 151 such as a Model No. 10 manufactured by Flotron Inc., Patterson, New Jersey.
  • the fuel flow through the transducer proceeds through a second pressure regulator 152 from which the pressure of fuel supplied to the carburetor is further stabilized and can be adjusted to the desired value.
  • the mass fuel flow through the transducer 151 provides a differential pressure output which is proportional to the mass flow.
  • differential pressure transducers 153, 154, and 155 are provided to sense this differential pressure and adequately cover the range of flow measurement on a laboratory carburetor flow bench.
  • the outputs of these transducers are current signals which are fed to the fuel pressure signal conditioners 156-158 respectively, which convert the current signals to voltage signals which are supplied to different sections of the A/D converter 105.
  • Digital outputs from the A/D converter are supplied to the computer interface 97 and then to the computer 28 for calculation of the mass fuel flow entering the carburetor.
  • FIG. 16 there is shown in a volumetric fuel flow transducer using a set of orifices.
  • the differential pressure across the orifices varies approximately in proportion to the square of the volumetric fuel flow through the orifices 165.
  • the differential pressure is sensed by a differential pressure transmitter 153 similar to that shown in FIG. 15.
  • a temperature probe 159 senses the temperature of the fuel entering the carburetor and supplies a resistance signal to the temperature signal conditioner 160 which supplies a voltage signal to an additional section of the A/D converter 105, which in turn provides a digital signal through the computer interface 97 and thus to the computer 28.
  • the fuel flow transmitter is a volumetric flow transducer sucha as Model No. 1214 manufactured by Fluidyne Instrumentation of Oakland, California, the output signal of which is a voltage signal which is proportional to the volumetric flow through the transmitter.
  • This voltage signal is fed to a signal conditioner 167 whose output is supplied to the A/D converter 105 as shown in FIG. 16.
  • FIG. 16 has the same second pressure regulator 152 as is present in FIG.
  • the second pressure regulator is not manually set for the particular fuel flow, but is controlled by the computer in response to a measurement of the actual fuel pressure present in the carburetor 73 at any given time.
  • a measurement of fuel pressure is obtained by a differential fuel pressure transmitter 168 having a first proble 198 and a second probe 199 which measures the difference between the pressure in the test chamber 88 and the fuel line 74.
  • a pressure signal from the differential fuel pressure transmitter 168 is supplied to the fuel pressure signal conditioner 169 which converts it to a current signal. This signal is in turn supplied to an additional section of the A/D converter 105 where it is changed from an analog into a digital signal which is supplied to the computer interface 97 and thus to computer 28 for the calculation of fuel pressure.
  • the computer 28 supplies an output signal to the computer interface 97 which converts the signal into one useable in the system.
  • the signal from the computer interface 97 will instruct the motor control circuit 170 to operate the motor in a direction that raises or lowers the fuel pressure in a manner to bring it closer to the desired value.
  • FIG. 28 a description of at least one method according to which the entire test stand may operate is felt mandatory for an understanding of the present invention.
  • a flow chart shown in FIG. 28 After starting the test, and depending on the particular test, whether it be a Balance Box carburetor test, a constant manifold vacuum test or a test at a specific manifold vacuum, and depending on the configuration of the equipment, and more particularly whether the system is equipped with a manifold vacuum bypass valve control the computer 28 will calculate as necessary the values or proportional band, reset time and derivative time which will give the optimum control possible for the hood pressure control valve 133, the manifold vacuum in-line valve 107 and the manifold vacuum bypass valve 108. From these values, the computer will then set the output for the first test point for the hood pressure, manifold vacuum in-line valve, manifold vacuum bypass valve (if used), the throttle position and the fuel pressure.
  • the computer 28 will calculate the hood pressure, the manifold vacuum, the mass air flow rate, the mass fuel flow rate, the fuel pressure and the air/fuel ratio.
  • the system will continue to recalculate the values of proportional band, reset time and derivative time, and will reset the outputs as described above and recalculate the values of hood pressure, manifold vacuum, mass air flow, mass fuel flow, fuel pressure and air/fuel ratio at approximately one-half second intervals until it is determined that the values for the particular test point are acceptable and have stabilized sufficiently so that the test can proceed.
  • the system has a built in cycle counter which is used to determine the number of readings that are used to determine the average.
  • the cycle counter When the test starts, the cycle counter will read zero and, if for example the average of ten readings are desired for the first test point, when the cycle counter equals ten the averaging process for the first test point will stop. In order to obtain these averages, if the cycle count is at zero, the system will look at the values for hood pressure, manifold vacuum, etc. and see if these values are acceptable.
  • the cycle counter will then add one to the cycle count and it will next check to see if the cycle count is equal to the total count desired. In this case, since the cycle count is one and the total count desired is ten, it is obvious that the cycle count is not equal to the total count desired. Therefore, the system will again pause for one-half second and it will calculate all the desired values again. Since the cycle count is not equal to zero the check to make sure all values are acceptable will not be performed, but instead one is again added to the cycle count and the process will continue until ten values for each desired quantity have been calculated. At this time the average of the ten values for each quantity are calculated, the results displayed and printed out for other use if desired, and the cycle counter set to zero in preparation to go to the next test point.
  • the system will add one to the cycle count and proceed to the calculation loop, for the calculation of the average hood pressure, manifold vacuum, mass air flow, mass fuel flow, fuel pressure, and air/fuel ratio.
  • the test experiences a minimum delay because it no longer checks to see if the values are acceptable, and the cycle counter will reach the total count rapidly, and the average values will be quickly calculated and displayed, even through the carburetor is not operating properly.
  • the system sets the cycle count to zero and is prepared to proceed to the next test point. If the test has been automated this is exactly what the system will do and the operation of the test system just described will be repeated for all test points.
  • the system can either shut itself down or can be left flowing at the particular test point, with it being the responsibility of the operator to stop the test or, if desired, repeat the test a number of times at the sametest point.
  • the present invention is able to test a carburetor far more accurately than was heretofore possible, and in a manner which is faster and more desirable than anything available in the prior art.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Control Of The Air-Fuel Ratio Of Carburetors (AREA)
US05/633,022 1975-11-17 1975-11-17 Method and apparatus for laboratory testing of carburetors Expired - Lifetime US4030351A (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
US05/633,022 US4030351A (en) 1975-11-17 1975-11-17 Method and apparatus for laboratory testing of carburetors
GB36813/76A GB1548953A (en) 1975-11-17 1976-09-06 Method and apparatus for laboratory testing of carubettors
DE2649682A DE2649682C2 (de) 1975-11-17 1976-10-29 Verfahren und Vorrichtung zur Prüfung von Vergasern
IT51977/76A IT1075996B (it) 1975-11-17 1976-10-29 Apparecchiatura per prova di laboratorio sui carburatori
JP51131570A JPS5275465A (en) 1975-11-17 1976-11-01 Method of and apparatus for testing carburetor
BE172319A BE848293A (fr) 1975-11-17 1976-11-12 Procede et banc d'essai de carburateurs,
CA265,673A CA1075493A (en) 1975-11-17 1976-11-15 Method and apparatus for laboratory testing of carburetors
FR7634508A FR2331784A1 (fr) 1975-11-17 1976-11-16 Procede et banc d'essai de carburateurs
AU19703/76A AU496906B2 (en) 1975-11-17 1976-11-17 Method and apparatus for laboratory testing of carburetors

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US05/633,022 US4030351A (en) 1975-11-17 1975-11-17 Method and apparatus for laboratory testing of carburetors

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US (1) US4030351A (de)
JP (1) JPS5275465A (de)
AU (1) AU496906B2 (de)
BE (1) BE848293A (de)
CA (1) CA1075493A (de)
DE (1) DE2649682C2 (de)
FR (1) FR2331784A1 (de)
GB (1) GB1548953A (de)
IT (1) IT1075996B (de)

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US4269062A (en) * 1979-10-10 1981-05-26 Colt Industries Operating Corp. Method for gauging fluid flow
US4296472A (en) * 1979-10-01 1981-10-20 Rockwell International Corporation Non-intrusive fluid measuring system
US4330828A (en) * 1978-07-21 1982-05-18 Scans Associates, Inc. Method of controlling production processes and apparatus therefor
US4343348A (en) * 1978-06-02 1982-08-10 The Allen Group Apparatus and methods for simulating varying atmospheric conditions
US4756186A (en) * 1984-12-14 1988-07-12 Honda Giken Kogyo Kabushiki Kaisha Input/output signal checker for an electronic control unit in an electronically controlled fuel injection system
WO1997011336A1 (en) * 1995-09-22 1997-03-27 The Scott Fetzer Company Inc. Apparatus for measuring exhaust flowrate using laminar flow element
US5633457A (en) * 1992-06-05 1997-05-27 Triangle Special Products Fuel injection cleaning and testing system and apparatus
US6349601B1 (en) 1999-06-10 2002-02-26 United Air Lines, Inc. Aircraft pneumatic system test cart
US20030061866A1 (en) * 2001-07-25 2003-04-03 Schneider Automation Inc. Mobile HVAC cavity test device, method, and computer product
US20030130815A1 (en) * 1999-11-05 2003-07-10 Adam Cohen Air flow sensing and control for animal confinement system
CN107387262A (zh) * 2017-06-12 2017-11-24 薛美英 化油器自动检测机
CN109915283A (zh) * 2019-03-25 2019-06-21 力帆实业(集团)股份有限公司 一种并列双腔化油器流量测试安装座
US10794333B2 (en) 2017-08-09 2020-10-06 Weaver Intellectual Property, LLC General aviation carburetor testing and analysis device
US11473532B2 (en) 2017-08-09 2022-10-18 Weaver Intellectual Property, LLC General aviation carburetor testing with turbocharger and analysis device
CN117212121A (zh) * 2023-09-04 2023-12-12 北京东方计量测试研究所 高真空泵抽速测试装置及其使用方法

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DE3227319C2 (de) * 1982-07-22 1984-07-12 Pierburg Gmbh & Co Kg, 4040 Neuss Prüfstand zur Einstellung von Gemischbildnern

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US3646600A (en) * 1969-07-09 1972-02-29 Holley Carburetor Co Method and apparatus for gauging fluid flow
US3691824A (en) * 1970-06-05 1972-09-19 Dynamic Precision Controls Cor Carburetor evaluation system
US3851523A (en) * 1970-10-16 1974-12-03 Scans Associates Inc Apparatus for testing carburetors

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US3520312A (en) * 1968-04-19 1970-07-14 Gen Motors Corp Flow process including viscosity control
DE1922902C3 (de) * 1969-05-06 1973-10-31 A. Pierburg Autogeraetebau Kg, 4040 Neuss Vorrichtung zur Einstellung und Prüfung von Vergasern fur Brennkraft maschinen
DE1936321C3 (de) * 1969-07-17 1980-11-06 Pierburg Gmbh & Co Kg, 4040 Neuss Vorrichtung zur Einstellung und Prüfung von Vergasern für Brennkraftmaschinen
BE790120A (fr) * 1971-10-16 1973-02-01 Aviat G M B H Procede et banc d'essai pour le controle et le reglage de carburateurs destines a des moteurs a combustion interne

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US3434341A (en) * 1966-07-28 1969-03-25 Holley Carburetor Co Carburetor test equipment
US3524344A (en) * 1968-09-19 1970-08-18 Scans Associates Inc Apparatus for testing carburetors
US3646600A (en) * 1969-07-09 1972-02-29 Holley Carburetor Co Method and apparatus for gauging fluid flow
US3691824A (en) * 1970-06-05 1972-09-19 Dynamic Precision Controls Cor Carburetor evaluation system
US3851523A (en) * 1970-10-16 1974-12-03 Scans Associates Inc Apparatus for testing carburetors

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4343348A (en) * 1978-06-02 1982-08-10 The Allen Group Apparatus and methods for simulating varying atmospheric conditions
US4330828A (en) * 1978-07-21 1982-05-18 Scans Associates, Inc. Method of controlling production processes and apparatus therefor
US4296472A (en) * 1979-10-01 1981-10-20 Rockwell International Corporation Non-intrusive fluid measuring system
US4269062A (en) * 1979-10-10 1981-05-26 Colt Industries Operating Corp. Method for gauging fluid flow
US4756186A (en) * 1984-12-14 1988-07-12 Honda Giken Kogyo Kabushiki Kaisha Input/output signal checker for an electronic control unit in an electronically controlled fuel injection system
US5633457A (en) * 1992-06-05 1997-05-27 Triangle Special Products Fuel injection cleaning and testing system and apparatus
WO1997011336A1 (en) * 1995-09-22 1997-03-27 The Scott Fetzer Company Inc. Apparatus for measuring exhaust flowrate using laminar flow element
US5837903A (en) * 1995-09-22 1998-11-17 The Scott Fetzer Company Inc. Device for measuring exhaust flowrate using laminar flow element
US6349601B1 (en) 1999-06-10 2002-02-26 United Air Lines, Inc. Aircraft pneumatic system test cart
US20030130815A1 (en) * 1999-11-05 2003-07-10 Adam Cohen Air flow sensing and control for animal confinement system
US20030061866A1 (en) * 2001-07-25 2003-04-03 Schneider Automation Inc. Mobile HVAC cavity test device, method, and computer product
US7010464B2 (en) * 2001-07-25 2006-03-07 Schneider Automation Inc. Mobile HVAC cavity test device, method, and computer product
CN107387262A (zh) * 2017-06-12 2017-11-24 薛美英 化油器自动检测机
US10794333B2 (en) 2017-08-09 2020-10-06 Weaver Intellectual Property, LLC General aviation carburetor testing and analysis device
US11473532B2 (en) 2017-08-09 2022-10-18 Weaver Intellectual Property, LLC General aviation carburetor testing with turbocharger and analysis device
CN109915283A (zh) * 2019-03-25 2019-06-21 力帆实业(集团)股份有限公司 一种并列双腔化油器流量测试安装座
CN109915283B (zh) * 2019-03-25 2023-07-04 力帆实业(集团)股份有限公司 一种并列双腔化油器流量测试安装座
CN117212121A (zh) * 2023-09-04 2023-12-12 北京东方计量测试研究所 高真空泵抽速测试装置及其使用方法
CN117212121B (zh) * 2023-09-04 2024-03-01 北京东方计量测试研究所 高真空泵抽速测试装置及其使用方法

Also Published As

Publication number Publication date
BE848293A (fr) 1977-03-01
GB1548953A (en) 1979-07-18
AU496906B2 (en) 1978-11-09
AU1970376A (en) 1978-05-25
DE2649682C2 (de) 1982-04-22
FR2331784A1 (fr) 1977-06-10
CA1075493A (en) 1980-04-15
IT1075996B (it) 1985-04-22
JPS5275465A (en) 1977-06-24
FR2331784B1 (de) 1980-07-04
DE2649682A1 (de) 1977-06-02

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